1. Technical Field
The present invention relates to a peg for a stringed instrument such as a guitar, and more particularly, relates to a peg for a stringed instrument in which the winding shaft rotates due to the tension of the string, and tuning is thereby made easy.
2. Background Art
The peg used in a stringed instrument such as a guitar generally comprises a worm gear provided coaxialy with respect to a knob, and a worm wheel which meshes with the worm gear and is provided coaxialy with respect to a winding shaft. In this type of peg, a large string tension acts on the winding shaft, and the string tension is often changed due to tuning of the string and choking made for a performance. In addition, because the peg must be mounted within a limited space at the head of the guitar, there are limitations with respect to the structure of the peg. Furthermore, since the peg is required to have a decorative appearance, the parts of the peg are often coated by plating or coating. For this reason, it is difficult to maintain the precision of size in the parts of the peg, and because of this situation, there have been problems hitherto with respect to the structure of the peg.
FIG. 7 shows a cross-sectional view of an example of a peg used in an electric guitar, a folk guitar, and the like. In the peg shown in FIG. 7, a main body 1 is mounted to a guitar head H, and a winding shaft 3 having a worm wheel 2 fixed to an end thereof is rotatably supported by the main body 1. A worm gear which meshes with the worm wheel 2 is rotatably supported by the main body 1, and a knob having the same axis as the worm gear is fixed to the worm gear (neither is shown).
The worm wheel 2 is closely fitted into the winding shaft 3 such that relative rotation with respect to an end portion thereof is prevented, and the worm wheel 2 is secured to the winding shaft 3 with a screw 4. In addition, a plate portion 1a of the main body 1 is disposed between the shoulder 3a of the winding shaft 3 and the bottom surface 2a of the worm wheel 2 with a gap. In addition, a screw 1b is formed on an inner surface of one end portion of the main body 1, and a securing nut 5 is screwed to the screw 1b. The winding shaft 3 is rotatably inserted through the securing nut 5.
In the peg described above, a leading end portion of the string is anchored at the string winding surface 3b of the winding shaft 3. When the knob is rotated, the string is wound. In the peg shown in FIG. 7, because the plate portion 1a of the main body 1 is disposed between the shoulder 3a of the winding shaft 3 and the bottom surface 2a of the worm wheel 2 with a gap there between them, the winding shaft 3 is rotatable in the direction of slackening due to the tension of the string. Accordingly, the surface of the teeth of the worm wheel 2 is always pressed in a set direction with respect to the surface of the teeth of the worm gear due to the string tension. This type of structure is used because in tuning, and the effects described in the following are achieved.
Specifically, when the string is tensioned, the winding gear 3 is rotated due to the surface of the teeth of the rotating worm gear being pressed against the surface of the teeth of the worm wheel. On the other hand, since the surface of the teeth of worm wheel 2 is pressed to the surface of the teeth of the worm gear in a constant direction, when the worm gear rotates in the direction of slackening of the string, the worm gear rotates along with the worm wheel 2 in the same direction. Accordingly, the string is slackened by the exact amount by which the knob is turned in real time, and this has the advantage that tuning is made easy.
Conversely, the conventional peg has a structure in which the plate portion 1a is tightened by shoulder 3a of the winding shaft 3 and the bottom surface 2a of the worm wheel 2. In this type of peg, since there is a large amount of frictional resistance between the winding shaft 3 and the main body 1, the winding shaft is not easily rotated by the string tension. Thus, if after the knob is rotated in one direction, and is rotated again in the opposite direction, there is a time lag corresponding to the amount of backlash of the worm gear and the worm wheel 2 generated between the time when the knob is first rotated until the time when the worm wheel 2 rotates. As a result, there is a problem in that tuning is difficult. In addition, after tuning in the direction of slackening of the strings has been completed, the worm gear may gradually rotate during backlash of the worm wheel 2 due to string tension, and the notes may become out of tune during performance. For this reason, at the time of tuning, a method must be used in which, the sound is adjusted while tensioning the string after the string has been sufficiently slackened, and this is the main reason why tuning is so difficult.
However, even in the winding device shown in FIG. 7, many kinds of problems have become apparent. That is to say, the gap between the plate portion 1a of the main body 1 and the worm wheel 2 and the shoulder 3a of the winding shaft 3 is set such that even if the winding shaft 3 becomes inclined due to the string tension, the winding shaft 3 never moves in the axial direction. However, the dimension of the gap may fluctuate with the precision of the processing or the thickness of the plating of the winding shaft 3 and the plate portion 1a. As a result, if the dimension of the gap is smaller than a set value, there is a large amount of frictional resistance between the winding shaft 3 and the main body 1, and thus, the same problems caused by backlash which are described in the foregoing occur.
On the other hand, if the distance of the gap is larger than the set value, a space is generated in the axial direction in which the winding shaft moves. For this reason when the direction of rotation of the worm gear changes, first the worm wheel 2 moves along with the winding shaft 3 in the axial direction, and when the winding shaft 3 reaches the moving end of the worm wheel 2, the rotation of the worm gear is transmitted to the worm wheel 2. That is to say, the gear is in the same state as it is when there is backlash. In addition, when the worm wheel 2 moves in the axial direction, the surface of the teeth thereof are abraded by the corners of the surface of the teeth of the worm gear, and as a result, errors in rotation are caused and a gap is formed between the surfaces of the teeth, thus hindering smooth rotation. Also, when the worm wheel 2 is forcibly rotated, the plate portion 1a bends, thus rendering the winding shaft unusable.
Furthermore, in the peg shown in FIG. 7 by providing the gap between the plate portion 1a of the main body 1 and the worm wheel 2 and also between the plate portion 1a of the main body 1 and the shoulder 3a of the winding shaft 3, the screw 4 must be fixed loosely. As a result, the screw 4 becomes even looser due to vibrations of the string at the time of performance, and due to sympathetic vibration, the screw may fall out. In an effort to eliminate this problem, the screw 4 has been fixed with an adhesive, but when this is done, repair of the peg becomes extremely difficult.
A peg in which a spring washer is disposed between a worm wheel and a plate portion has also been provided. In this type of peg, movement of the winding shaft in the axial direction is controlled and rotation due to string tensioning becomes possible. However, the material for forming the main body is generally made from a diecast product of soft metals such as aluminum or zinc or brass, or the like. As a result, there is a problem in that the spring washer which is caused to rotate along with the worm wheel shaves the main body. Furthermore, the axial direction position of the worm wheel may vary in accordance with the strength with which the screw is tightened, and more particularly, in a drum-shaped worm wheel, if the axial direction position is shifted, normal meshing of the worm wheel and the worm gear cannot be ensured, and thus there is abnormal wearing of the surface of the teeth. In addition, because the worm wheel is disposed on top of the spring washer, there is a tendency for the winding shaft and the worm wheel to tilt due to the string tension and this too interferes with the normal meshing of the gear.
By forming the closely fitting portion of the worm wheel and the winding shaft in a non-circular shape, relative rotation thereof is prevented. Ideally, there should be no gap between the worm wheel and the winding shaft when both are fitted each other. However, in consideration of variations in processing precision and in the thickness of the plating, a clearance is provided to a certain extent in which assembly is not hindered. As a result, there is idle in the direction of rotation between the worm wheel and the winding shaft, and as in the case of backlash of the gear, a time lag is generated in tuning.
FIG. 8 is a cross-sectional view of an example of another type of peg known as the bushing type. A main body 10 is mounted to the guitar head H by a screw, and a worm wheel 12 having a winding shaft 11 fixed to one end thereof is rotatably supported by a main body 10. A worm gear 13 having a knob (not shown) mounted to one end thereof is rotatably supported by the worm wheel 12. In addition, a hole 14 is formed in the head H, and a bushing 15 for guiding the winding shaft 11 is fit into the hole 14.
In this type of peg, it is difficult for the center of the hole 14 and the center of the winding shaft 11 to be brought together. In particular, in pegs in which a plurality of winding shafts are provided to one main body, and it is extremely difficult to coincide the centers of all the winding shafts with the holes of the head. In addition, in a guitar such as a classical guitar in which the mounting surface of the main body is tapered, in order to pass the winding shaft through the mounting surface, it is necessary to form a hole perpendicularly to the center line of the head. As a result, the distance of gaps easily vary, and moreover, the hole tends to be formed with a bend. As a result, as shown in FIG. 8, the winding shaft 11 and the worm wheel 12 are supported in an inclined condition. Consequently, there is a large amount of frictional rotation of the winding shaft 11 and the bushing 15, and thus the winding shaft 11 is not easily rotated due to the string tension. Accordingly, similar problems to those described above which are caused by the backlash of the gears, are generated. Furthermore, as shown in FIG. 8, because the winding shaft 11 is inclined, there are problems in that the normal meshing of the worm wheel 12 and the worm gear 13 cannot be maintained and the surface of the teeth wear abnormally, or the edge of the worm gear 12 comes into contact with the inner surface of the main body 10 and a large force must be exerted in order to carry out tuning.
The present invention was completed by studying the problems described above, and an object of the present invention is to provide a peg in which the winding shaft can be rotated due to string tension and tilt of the winding shaft and movement of the winding shaft in the axial direction are controlled, thus solving the various problems described above.
A peg for a stringed instrument comprising, a main body mounted to the head of the stringed instrument, a worm wheel rotatably supported by the main body and having a winding shaft at one end portion, a worm gear rotatably supported by the main body, the wormgear meshing with the worm wheel and having a knob at one end portion thereof, a hole formed in the worm wheel and having a portion with a non-circular cross-section, a winding shaft main body formed in the winding shaft so as to wind a string, a closely fitting portion formed in the winding shaft and having a smaller diameter than that of the winding shaft main body, the closely fitting portion passing through a plate portion of the main body and closely fitting into the portion with the non-circular cross-section, a tightening device inserted in the hole and screwed to the closely fitting portion, wherein an axial cross-section of the closely fitting portion is slightly larger than an axial cross-section of the hole, and the closely fitting portion is pressed into the hole by tightning the tightening device.
In the peg having the above-described structure, because the closely fitting portion of the winding shaft is pressed into the hole in the worm wheel, there is no gap between the closely fitting portion and the hole. Accordingly, when the worm wheel is rotated by the worm gear, this rotation is transmitted in real time to the winding shaft. In addition, even if there are variations in the thickness of the plate portion of the main body caused by manufacturing error or variation in the thickness of the plating, by adjusting the amount by which the tightening means is tightened, the gap between plate portion and the worm wheel and also between the plate portion and the winding shaft main body can be fixed. Thus, by causing the gap to have the optimum dimension, the winding shaft can maintain a state in which it is rotated by the string tension, and also movement of the winding shaft in the axial direction and tilting thereof is controlled. Accordingly, in the winding device of the present invention, when the guitar is being tuned, the winding shaft is not affected by the backlash of the gears or any other type of idle, and the winding shaft can be rotated by the knob in real time. As a result, tuning becomes easier and moreover, the precision of the tuning is improved. Also, in the present invention, because the closely fitting portion is pressed into the hole by the tightening means being tightened, there is an advantage in that there is a great resistance to the rotation of the tightening means, and thus it is difficult for the tightening means to become loose.
It is preferable that the length of the closely fitting portion pressed into the hole be 0.1 to 0.4 mm. If the length of the closely fitting portion pressed into the hole is less than 0.1 mm, then the fixing force is insufficient, and thus both the worm wheel and the winding shaft rotate relative to each other due to moment generated between the two. In addition, a length of the closely fitting portion pressed exceeding 0.4 mm is undesirable since a large force is required in order to tighten the tightening means, and also a large internal stress is generated in the worm wheel. The length of the closely fitting portion to be pressed into the hole is more preferably 0.2 to 0.3 mm. For the same reasons described above, it is preferable that the axial cross-section of the closely fitting portion in the radial direction be larger than the axial cross-section of the hole in the same direction by 0.005 to 0.2 mm, and more preferably by 0.05 to 0.13 mm. Furthermore, the gap between plate portion and the worm wheel and between the plate portion and the winding shaft main body is preferably 0.1 to 0.2 mm, and by providing this gap, the winding shaft can be rotated smoothly by the string tension, and also inclination of the winding shaft or movement of the winding shaft in the axial direction is such that it is not problematic in most cases. It should be noted that this gap can be obtained by setting the length of the closely fitting portion to be 0.3 to 0.5 mm longer than the thickness of the plate portion, and pressing the closely fitting portion into the hole to a depth of 0.2 to 0.3 mm.
The portion of the closely fitting portion for introduction into the hole may be formed with a tapered configuration with the taper in the direction of the tightening means side. However, in this type of structure, when the closely fitting portion is pressed into the hole, the worm wheel transforms so as to expand, and thus it is difficult for the closely fitting portion and the worm wheel to maintain normal meshing. Accordingly, it is preferable that the portion of the closely fitting portion for introduction into the hole be formed so as to have a step portion which has a larger diameter than the end portion at the tightening means side, and this step portion shaves off the inner wall of the hole and is thereby fit into the hole. That is to say, the end portion is caused to be fastened into the hole, and by doing this, transformation of the worm wheel is controlled, and also the fixing strength of the closely fitting is increased. It should be noted that the length of the closely fitting portion pressed into the hole is controlled by using a tool, such as torque driver, which can set the torque at the time when the tightening means is being tightened.
Next, the second peg of the invention has, a main body for mounting at the head portion of the stringed instrument, and a worm wheel which was rotatably supported by the main body and having a winding shaft at one end portion, and a worm gear which was rotatably supported by the main body and having a knob at one end portion, and which was meshed with the worm wheel, and a hole having a portion with a non-circular cross-section is formed in the worm wheel, and a winding shaft has a winding shaft main body and a closely fitting portion, and string is wound around the winding shaft main body, and the closely fitting portion was passed through the plate portion of main body and has a smaller diameter than the winding shaft main body, and the closely fitting portion being screwed in by being closely fitted in the portion of the hole having a non-circular cross-section and then inserting the tightening means into the hole, wherein an elastic member and a flat washer are disposed, in that order, between the plate portion and the winding shaft main body, from the winding shaft main body toward the plate portion.
In the peg having the above-described structure, the plate portion of the main body is nipped between the worm wheel and the winding shaft main body by the elasticity force of an elastic member. By suitably selecting the elasticity force of the elastic member, the winding shaft can be rotated smoothly by the string tension, and movement of the winding shaft in the axial direction, and inclination thereof and the like is controlled. In addition, in the above structure, the right angle of the winding shaft with respect to the plate portion can be tightened. Thus, even in the bushing type peg specifically, in which the center of the bushing easily shifts with respect to the winding shaft, it is unlikely that the winding shaft will be mounted in a state in which it is tilted.
In the present invention, an elastic member and a flat washer are disposed between the plate portion and the winding shaft, in that order, and this is an important feature of the invention. That is to say, with this structure, because the bottom surface of the worm wheel is disposed on top of the plate portion of the main body, it is unlikely that that the winding shaft will tilt. In addition, because the plate portion is nipped between the worm wheel and the flat surface of the flat washer, it is even less likely for the winding shaft to tilt. Furthermore, since the winding shaft which has a smaller diameter than the worm wheel does not generally contact the plate portion directly, wearing of the plate portion caused by rotation of the winding shaft is prevented. Accordingly, in the second winding shaft of the present invention also, when the guitar is being tuned, the winding shaft is not affected by the backlash of the gears or by any other type of idle, and the winding shaft can be rotated by the knob in real time. As a result, tuning becomes easier, and moreover, the precision of the tuning is increased. It should be noted that this effect is even greater if a flat washer similar to that described above is disposed between the winding shaft main body and the elastic member.
The elastic member is preferably a plate-spring. Examples of elastic members which may used, other than a plate spring, are: a spring washer having a wave configuration in the circumferential direction thereof; a coil spring; and a washer formed of an elastic material such as rubber or synthetic resin. The flat washer is preferably a synthetic resin washer or metal washer having a lubrication coat on the surface thereof. Specific examples include: a synthetic resin including a polyacetal resin having no less than 10% by weight of polytetrafluoroethylene; a metal washer having solidifying lubricant such as molybdenum disulphide or the like coated on the surface thereof; or a metal washer on whose surface a mixed coat was disposed by coating with a dispersion solution of a plating solution and Teflon Resin (trademark). By using this type of flat washer, frictional resistance of the plate portion and the flat washer is reduced, and wear of the plate portion is also controlled.
The above-described features of the second invention may be favorably provided along with feature of the first invention. That is to say, in the first invention, in the case where the length of the closely fitting portion which is pressed into the hole is controlled by the tightening force of the tightening means, due to variation of the winding shaft processing precision, variation of the hardness of the worm wheel, or variation in the thickness of the plating, even when the tightening means is tightened with the same force, variation in the length of the closely fitting portion which is pressed in is generated. As a result, the length of the closely fitting portion pressed in may be increased and the plate portion is tightened more intensely by the winding shaft main body and the worm wheel. Thus the winding shaft can no longer be easily rotated due to the string tension. On the other hand there is the concern that idle of the winding shaft in the axial direction and inclination of the winding shaft will be generated if the length of the closely fitting portion which is pressed in is short. To solve this problem, it is preferable that the axial cross-section of the closely fitting portion be made slightly larger than the axial cross-section of the hole, and that by the tightening means being tightened, the closely fitting portion be pressed into the hole, and also that an elastic member and a flat washer be disposed, in this order, between the plate portion and the winding shaft main body, from the winding shaft main body toward the plate portion.